When enabling stack trace via "echo 1 > /proc/sys/kernel/stack_tracer_enabled", the below KASAN warning is triggered:

BUG: KASAN: stack-out-of-bounds in check_stack+0x344/0x848 at addr ffffffc0689ebab8 Read of size 8 by task ksoftirqd/4/29 page:ffffffbdc3a27ac0 count:0 mapcount:0 mapping: (null) index:0x0 flags: 0x0() page dumped because: kasan: bad access detected CPU: 4 PID: 29 Comm: ksoftirqd/4 Not tainted 4.5.0-rc1 #129 Hardware name: Freescale Layerscape 2085a RDB Board (DT) Call trace: [<ffffffc000091300>] dump_backtrace+0x0/0x3a0 [<ffffffc0000916c4>] show_stack+0x24/0x30 [<ffffffc0009bbd78>] dump_stack+0xd8/0x168 [<ffffffc000420bb0>] kasan_report_error+0x6a0/0x920 [<ffffffc000421688>] kasan_report+0x70/0xb8 [<ffffffc00041f7f0>] __asan_load8+0x60/0x78 [<ffffffc0002e05c4>] check_stack+0x344/0x848 [<ffffffc0002e0c8c>] stack_trace_call+0x1c4/0x370 [<ffffffc0002af558>] ftrace_ops_no_ops+0x2c0/0x590 [<ffffffc00009f25c>] ftrace_graph_call+0x0/0x14 [<ffffffc0000881bc>] fpsimd_thread_switch+0x24/0x1e8 [<ffffffc000089864>] __switch_to+0x34/0x218 [<ffffffc0011e089c>] __schedule+0x3ac/0x15b8 [<ffffffc0011e1f6c>] schedule+0x5c/0x178 [<ffffffc0001632a8>] smpboot_thread_fn+0x350/0x960 [<ffffffc00015b518>] kthread+0x1d8/0x2b0 [<ffffffc0000874d0>] ret_from_fork+0x10/0x40 Memory state around the buggy address: ffffffc0689eb980: 00 00 00 00 00 00 00 00 f1 f1 f1 f1 00 f4 f4 f4 ffffffc0689eba00: f3 f3 f3 f3 00 00 00 00 00 00 00 00 00 00 00 00

ffffffc0689eba80: 00 00 f1 f1 f1 f1 00 f4 f4 f4 f3 f3 f3 f3 00 00

^ ffffffc0689ebb00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffffffc0689ebb80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

The stacker tracer traverses the whole kernel stack when saving the max stack trace. It may touch the stack red zones to cause the warning. So, just disable the instrumentation to silence the warning.

Signed-off-by: Yang Shi yang.shi@linaro.org --- kernel/trace/trace_stack.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c index 202df6c..61e5e1e 100644 --- a/kernel/trace/trace_stack.c +++ b/kernel/trace/trace_stack.c @@ -156,7 +156,7 @@ check_stack(unsigned long ip, unsigned long *stack) for (; p < top && i < stack_trace_max.nr_entries; p++) { if (stack_dump_trace[i] == ULONG_MAX) break; - if (*p == stack_dump_trace[i]) { + if ((READ_ONCE_NOCHECK(*p)) == stack_dump_trace[i]) { stack_dump_trace[x] = stack_dump_trace[i++]; this_size = stack_trace_index[x++] = (top - p) * sizeof(unsigned long);